ANAT241 L2 Flashcards
What are the 4 different modes of cell signalling?
- juxtacrine
- autocrine
- paracrine
- endocrine
What is required for the juxtacrine mode of signalling?
- direct cell-cell contact
- may be mediated by gap junctions
What is a gap junction composed of
- composed of proteins called connexions
What is a key feature of a gap junction?
bi-directional
What are the 3 key functions of a gap junction?
- allow ions and small molecules to move between cells
- provide electrical and chemical coupling between cells
- allow very rapid communication between groups of cells, e.g. cardiac muscle cells
How is juxtacrine specifically achieved?
by direct contact
What are 2 functions of juxtacrine?
- can involve receptors
- can deliver more complex information
What are 2 features of juxtacrine’s signal molecule?
- is not released
- membrane bound
What is juxtacrine important in?
development
How is juxtacrine specificity achieved?
by receptor expression AND direct contact
What is an example of a juxtacrine?
notch pathway
What is the main role of autocrine?
signalling between nearby cells of the same type
What are 2 functions of autocrine?
- release and reception of signal molecule
- can coordinate activity between a group of similar cells
How is specificity achieved?
by selective receptor expression and rapid degradation of signal molecule
What is the main role of paracrine?
local signalling between different cell types
What is required for paracrine to occur?
the release and reception of signal molecules
What is an example of the release and reception of signal molecules in paracrine?
endothelial cells communicate with nearby vascular smooth muscle via release of nitric oxide
How is specificity achieved in paracrine signalling?
by selective receptor expression and rapid degradation of signal molecule
What occurs during neuronal signalling?
- signal molecules are neurotransmitters
- released from neurone and specialised highly localised synaptic sites
What type of effect is created during neuronal signalling?
rapid and often short-lasting effects
How is specificity achieved in neuronal signalling?
by precise contacts and rapid removal of neurotransmitter to prevent diffusion
How does endocrine signalling occur?
usually involves signalling between distant cells
What are signals called in endocrines, how are they carried and where are they produced?
signals are called hormones, and are carried in the blood
Where are the signals, in endocrine, produced?
produced from endocrine glands, tissues and isolated cells
How is endocrine produced?
produced from endocrine glands, tissues and isolated cells
Endocrine signalling involves many types of hormones, what are some examples?
steroids, modified amino acids and peptides
How is specificity achieved?
by selective receptor expression
What type(s) of signalling is required in selective receptor expression?
What type(s) of signalling is required in rapid uptake/degradation of signal?
What type(s) of signalling is required in direct contact?
What needs to happen to signal molecules, with regards to the target cell?
signal molecules need to be produced, released, and transported to the target cell
What is a ligand?
a molecule that binds specifically to another molecule
What are the 3 types of …
- lipid soluble
- water soluble
- gases (e.g. nitric oxide)
What happens to signal molecules with regard to …
interact with protein on target cell: the receptor
specific ligands bind to specific receptors
How are water soluble ligands stored?
can be stored in vesicles within cell
How are lipid soluble ligands stored?
cannot be stored in vesicles within cell
What is the rate of release of water soluble ligands?
rapid release via exocytosis
What is the rate of lipid soluble ligands?
slow response - made on demand
How do water soluble ligands travel?
can travel in blood without a carrier
How do lipid soluble ligands travel?
travels in blood with carrier protein (may be longer lasting)
Where can/can’t water soluble ligands enter?
cannot enter target cell (message transduce via cell surface receptor)
Where can/can’t lipid soluble enter?
can enter target cells by crossing membrane
What do lipid soluble ligands act on?
intracellular receptors (often to directly regulate gene expression)
What are some common ligands?
hormones, growth factors and neurotransmitters
How do hormones travel?
in the blood
What are some examples of common ligands?
testosterone, estradiol, insulin, glucagon
What is the function of growth factors?
stimulate cell proliferation, wound healing
What is a growth factor normally seen as?
normally a protein or steroid hormone
What is an example of some growth factors?
IGF1 (skeletal muscle hypertrophy), cytokines (fas = apoptosis)
How does a neurotransmitters occur?
sent across a synapse
What are some examples of neurotransmitters?
acetylcholine (activates skeletal muscle), epinephrine (acts on blood vessels)
What are the 2 types of signal receptors?
intracellular and extracellular
Where are intracellular signal receptors located?
receptor protein located inside cell (nucleus, cytoplasm)
What
ligands need to be lipid soluble
What do intracellular signal receptors do?
usually alter gene expression
Where are extracellular signal receptors found?
ion channels
What are some examples of extracellular signal receptors?
- g-protein coupled receptors
- enzyme-linked receptors (cytokine receptors)
What do extracellular signal receptors do?
- change membrane conductance
- alter protein activity
- regulate cellular events
What must be noted about signal receptors?
different receptors for different pathways
